1. Field of the Invention:
The present invention relates to an automatic joining apparatus for automatically joining an attachment start edge and an attachment finish edge of a carcass ply cut into a length somewhat shorter than a circumferential length of a former drum and wound around an outer circumferential surface of the former drum.
2. Description of the Prior Art:
At first, an apparatus for attaching a carcass ply onto a former drum in the prior art will be explained with reference to FIG. 11. In this figure, reference character (a) denotes a former drum, character (b) denotes a tray, character (c) denotes a carcass ply, character (d) denotes an intermediate table, character (e) denotes a festoon, character (f) denotes a liner roll, character (g) denotes a stock roll, character (h) denotes a let-off and character (F) denotes a floor surface. The carcass ply (c) is paid off from the stock roll (g) through the path consisting of the festoon (e).fwdarw.the intermediate table (d).fwdarw.the tray (b), an attachment start edge portion of the carcass ply (c) is attached onto the former drum (a) by hand work of an operator, and when the former drum (a) has revolved one revolution and the carcass ply has been wound around the former drum (a), the carcass ply is cut at a location between one cord (c.sub.1) and an adjacent cord (c.sub.1) by means of a heated knife or the like. Subsequently, the attachment start edge and the attachment finish edge of the carcass ply are joined to each other while adjusting the seam so that unevenness may not occur in the amount of lap of the seam, and then the joined portion is pressed by means of a hand roller.
In the carcass ply attaching apparatus in the prior art shown in FIG. 11, when the former drum (a) has revolved one revolution, the carcass ply is cut by means of a heated knife or the like at the location between one cord (c.sub.1) and an adjacent cord (c.sub.1), but with respect to an ideal cut line consisting of a straight line passing through center points of the intervals between adjacent cords, a passageway of the heated knife would be displaced, hence the carcass ply (c) would be cut along a line deviated to either direction from the ideal cut line, and so, a cut length (L.sub.2 in FIG. 12) of the carcass ply (c) would have an error of the order of .+-.1/2 of the pitch of the cord array with respect to a length (L) of a standard configuration. In addition, the carcass ply (c) after cutting would have local expansion or contraction in addition to overall expansion or contraction, and due to these expansion or contraction also, the attachment start edge and the attachment finish edge would not become straight. Consequently, an amount of lap of the seam between the attachment start edge and the attachment finish edge becomes uneven, and in the event that the amount of lap is insufficient, a joining strength is lowered, hence upon enlargement of a diameter during a shaping process, the joined portion is separated, and a scrap tire called "open cord" is produced. In addition, since an error arises at the cut portion and the attachment start edge and the attachment finish edge of the carcass ply (c) do not become straight, the cords (c.sub.1) would intersect or a density of cords (c.sub.1) would increase, and in this case also, the problem was present that scrap tires are produced.